Ethylene Inhibition of Ammonium Oxidation in Soil
1992
Porter, Lynn K.
Small quantities of ethylene (C₂H₄) are produced by bacteria and fungi in soils. Ethylene is produced when nitrogenase activity is measured by acetylene (C₂H₂) reduction. Acetylene has been used as a nitrification inhibitor and has been shown to produce C₂H₄ in flooded rice soils. Whether C₂H₄ affects the oxidation of NH₄ by the soil's nitrifying organisms and at what concentrations was the focus of this study. A Weld clay loam surface soil (fine, montmorillonitic, mesic Aridic Paleustoll) was treated with (NH₄)₂SO₄, subjected to various partial pressures of C₂H₄ and incubated at 30 °C. At designated incubation times, the atmospheres of the incubation flasks were analyzed for O₂, CO₂, and C₂H₄ by gas chromatography (GC) and the soil was analyzed for NH₄, and NO₃ plus NO₂ by steam-distillation procedures. At a C₂H₄ partial pressure of 0.017 kPa, NH₄ oxidation was similar to untreated samples. At a C₂H₄ partial pressure of 0.17 kPa, NH₄ oxidation was partially inhibited and, at a C₂H₄ partial pressure of 4.55 kPa, inhibition was nearly complete.
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